With 802.11ac Wave 2 in the house, wireless LAN (WLAN) customers are being courted by vendors and value added resellers with promises of enormous throughputs and fantastic features. It's an exciting time for everyone who sells, installs or uses Wi-Fi, but I'm here to tell that all is not what it seems. I've been doing wireless networking every day for more than 15 years, and I have seen many a hype cycle come and fade, with the next big high-speed wireless access thing always right around the corner.

What I'm about to share isn't meant to burst bubbles or kill a good Wi-Fi buzz -- but, every now and then, an injection of reality is good for everyone. Call it management of expectations or just putting a finer point on things, but as Paul Harvey used to say, we need to hear the rest of the story.

802.11ac is huge, but it's fickle

I just finished reading one vendor's promotional material on their high-speed wireless access Wave 2 gear. If you take it as delivered, every client device that hits the 802.11ac Wave 2 network will "get" 1.7 Gbps. That's it: You'll get that every time.

Call it management of expectations or just putting a finer point on things, but as Paul Harvey used to say, we need to hear the rest of the story.

First of all, there's no real clarity to what that even means. Too many WLAN vendors don't differentiate between data rates and throughput. In this case, we're talking data rates. But this is Wi-Fi, and it's still shared media, just like it has been since the original 802.11 standard first brought 1 and 2 Mbps data rates. And just as you had to cut those original data rates in half to get approximate throughputs, you have to do the same with the latest high-speed wireless access standards. It's not quite that cut and dry, but it's still a good rule of thumb: whatever your data rate is in Wi-Fi will be roughly double what your achievable throughput is. So, a 1.7 Gbps data rate gets you around 850 Mbps of throughput in a perfect world. But as they like to say, there's more.

A quick aside: If you actually can get that 1.7 Gbps data rate, and you expect to realize that ballpark 850 Mbps, it's all going to depend on what your network destination is. If you're connected to a local server, that's one thing. Heading off to the internet? If the pipe out doesn't have the capacity, you're at the mercy of the capacity that it does have. You might have a huge data rate, but the internet is a frequent bottleneck. Reality is reality.

For high speed to work, many factors come into play

Let's get back to that Wave 2 high-end throughput thing. It is amazing that we're using the Gigabit suffix with wireless data rates at all; it really is. And properly designed 802.11ac high-speed wireless access cells will be better than past Wi-Fi technologies every time.

But a lot of factors need to line up before you'll get the high-end numbers showing in your wireless utility. First, you'll need to have a client adapter that matches the radio capabilities of the access point (AP). If a 4x4 (Editor's note: four transmitters and four receivers) AP can push that 1.7 Gbps, you'll need a 4x4 client (Editor's note: four transmitters and four data, or spatial, streams) to match. And those don't generally exist right now. So, let's say you have a really good 3x3 laptop. That'll get you a top end data rate of around 1.3 Gbps. A good mobile device that can only do 1x1 won't deliver anything above 100 Mbps, even under ideal conditions. See how that contextless 1.7 Gbps thing doesn't really stand up?

It gets worse.

High-speed wireless access performance also relies on a number of configuration and environmental factors. Signal bars aren't enough. If you can't achieve good enough signal-to-noise ratio, your client can't achieve the sophisticated modulation types required for the highest rates. And those high-speed wireless rates also require wider channels than most WLAN experts recommend using in dense wireless environments. Wide channels mean less usable channels in Wi-Fi's allotted spectrum, and effective channel reuse is crucial to the dense WLAN environments typical in many business Wi-Fi scenarios. It's complicated, highly variable and often confusing to the outsider.

It's not really lying, but it ain't exactly the truth

Our reality is that Wi-Fi marketing is often at odds with good design practices and the realities of networking that happens over the air. I've heard marketers say things like, "It's too complicated to explain in detail," and, "Everyone says the same stuff; don't worry about it." Perhaps they're right on both accounts, but those who install high-speed wireless access know that, at minimum, the whole truth isn't told when big numbers are dropped in the PR materials with no backing context. WLAN users deserve to know Wi-Fi reality, too. It's a nuanced, variable reality that transcends most anything you'll read in marketing materials.

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